Aim: The aim is to evaluate the antibacterial activity of Cissus quadrangularis (CQ) extract and calcium hydroxide against Streptococcus mutans and Lactobacillus acidophilus. Materials and Methods: The ethanolic extract of CQ was obtained by Soxhlet method. The antibacterial activity of CQ extract and calcium hydroxide powder in three different solvents (saline, glycerol, and olive oil) was evaluated by agar well-diffusion method. The zones of inhibition formed against S. mutans and L. acidophilus were measured. Results: CQ in saline showed zone of inhibition against both S. mutans and L. acidophilus, whereas in olive oil, zone of inhibition was evident only against L. acidophilus. Calcium hydroxide exhibited zone of inhibition against S. mutans when dissolved in saline and glycerol. On the other hand, zone of inhibition against L. acidophilus was evident only in glycerol. Calcium hydroxide showed maximum zone of inhibition against both the microorganisms compared to CQ. Conclusion: CQ showed antibacterial activity against both S. mutans and L. acidophilus, but it was not comparable to calcium hydroxide.